Now in the modern days, the phrase "lets settle this like men" would imply a fist fight. Yet as little as 200 years ago, "settling it like men" would either involve swords or pistols; the fist was the tool of the peasants and the lower class. When and how did it become socially unacceptable to use weapons to 'settle' accounts?
France seems to hung on to the tradition longer than other places. It was still occurring in France with regularity before ww1. Perhaps it the slaughter of ww1 brought about the sharp decline after the war.
Georges Clemenceau french leader during war fought duels 1892,duelled the author and Boulangist Paul Déroulède with pistols.
http://en.wikipedia.org/wiki/Duel#Decline The last duel in France took place in 1967 when Gaston Defferre insulted René Ribière (fr) at the French parliament and was subsequently challenged to a duel fought with swords.
http://en.wikipedia.org/wiki/List_of_famous_duels#French_duels February 1897: Marcel Proust fought journalist Jean Lorrain, after Lorrain published an excoriating review of Proust's first book "Pleasures and Days" and hinted that Proust was having an affair with Madame Alphonse Daudet's son, Lucien.